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Volcanoes Chapter 4 Part 2 Volcanic gases Up to 9% of composition Water vapor [can be 50 – 80%] A primary source of original oceans (also comets) Carbon dioxide Sulfur dioxide Hydrogen sulfide Lesser gases HCl, HF, Cl Form vesicles when trapped in lava

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volcanoes chapter 4 part 2 volcanic gases
Volcanoes Chapter 4 Part 2Volcanic gases
  • Up to 9% of composition
  • Water vapor [can be 50 – 80%]
    • A primary source of original oceans (also comets)
  • Carbon dioxide
  • Sulfur dioxide
  • Hydrogen sulfide
  • Lesser gases
    • HCl, HF, Cl
  • Form vesicles when trapped in lava
mount unzen japan one of 75 active volcanoes in japan
Mount Unzen, Japanone of 75 active volcanoes in Japan

On island of

Kyushu

1991 eruption – ash flows at 200 km per hr; 1792 eruption killed 15,000

lake nyos cameroon africa 1986 event
Lake Nyos, Cameroon, Africa1986 event

Landslide and convective overturn

of lake water released CO2

3000 cattle and 1700 people died

mt pinatubo 1991
Mt Pinatubo 1991

Aerosols, extra fine particles, remained in atmosphere for one year

fig 7 08

Fig. 7.08

Stephen Marshak

fig 7 10

Fig. 7.10

Scoria cones are hills of basalt and andesite pyroclastic material produced by a single eruption

fig 7 12a

also much wider than high

Shield volcano – note low angles on flanks

Fig. 7.12a

W. W. Norton

fig 7 13

Fig. 7.13

W. W. Norton

calderas large volcanic craters
Calderas large volcanic craters

Examples include Crater Lake, OR;

Yellowstone NP, WY; Jemez caldera, NM

which type of structure is this
Which type of structure is this?

What characteristics tell you it is that particular structure?

flood basalts
Flood basalts
  • Low viscosity covering immense areas
  • Large volume of basalt
    • Siberia – 3 million cu km about 250 My ago
      • Major effect on life at the time
    • Deccan plateau [India] – 1.5 million cu km about 65 My ago
      • Added to meteorite impact, this caused problems!
    • Columbia River [Pacific NW] – 1.2 million cu km about 10 My ago
fig 7 18a

Fig. 7.18a

W. W. Norton

volcanic hazards
Volcanic hazards
  • Pyroclastic debris – flows, ash, pumice, lapilli
  • Blast – both vertical and lateral
  • Landslides
  • Lahars
  • Earthquakes and tsunami
  • Gas
  • Climatic changes due to particulates
slide22

Tectonic action in the

Pacific Northwest

Subducting slab is only

8 my old

Evidence of M 9 EQ in 1700

Top of Juan de Fuca plate and

the N American continent are

locked together—holding stress

mt rainier wa
Mt Rainier, WA

Potential major eruption

or landslide

Highest peak in Cascades

Problems

Great height

Largest ice pack in lower 48 states

Hot water spring system under surface

Photo by D Best

slide29

Mitigate the hazard

    • Forecasting an eruption by using
      • seismic data
      • thermal changes
      • surface tilting and swelling
      • volcanic gas emissions
      • past history